The present invention is directed to providing a belt scraper which is relatively low in cost and simple in construction in comparison to many conventional belt scraper apparatuses. For example, one more complex belt scraper employs a closed parallelogram linkage of four links having an internal, inflatable diaphragm to bias the links and a belt scraper blade against the underside of a conveyor belt. Such a system is relatively complex in that it requires a source of compressed gas to inflate the diaphragm and protective flaps to deflect the scrap debris from clogging the parallelogram linkages. The parallelogram linkages comprise four pivotally connected, steel link members two of which are generally horizontal, and the other two of which are generally inclined to the vertical. As the belt wears the tip away, the diaphragm pushes the linkages to raise the blade tip to continue scraping pressure against the conveyor belt. It will be appreciated that wet material, dirt and clays or sands or gravel or other caustic materials being conveyed by the conveyor belt can deposit in or about the linkages and interfere with the operation of the linkages. Also, the initial cost of a particular linkage and the gas bag add to the cost and the maintenance problems associated with this particular system.
The present invention is also directed to providing a belt scraper that is usable with belts spliced with mechanical belt splices made of metal belt fasteners. These metal belt fasteners strike the belt scraper, unless a mechanism is provided to lower the belt scraper upon approach of the belt fasteners. The belt scraper's striking of the metal fasteners can damage the splice, gouge the scraper blade and vibrate the scraper blade and generate noise. There is a need for a more fastener-friendly belt scraper that allows downward travel of the scraper blades and a cushioning of the impacts between the belt scrapers and the metal belt fasteners.
Another form of belt scraper device, such as disclosed in U.S. Pat. No. 3,841,470, uses an elastomeric block of solid rubber or synthetic resin to mount the blade. The blade holder includes a vertical plate fixed to a vertical face of the block; and there is a mild elastic deformation of the resilient member to provide the biasing force. This system does not provide much cushioning because of its rigidity. Further, this system does not maintain the blade pressed against the belt with sufficient force with wear of the scraper blade so that frequent force adjustments are necessary. It is most desirable that blade pressure be maintained without frequent adjustments or other kinds of maintenance.
It will be appreciated that belt scrapers for conveyors are often exposed to ambient weather conditions which can be either very hot during summertime or very cold in wintertime. Preferably, the belt scraper functions adequately in very cold temperatures where ice and snow accumulations may be formed on the conveyor belts and scrapers in addition to the dirt, clay, sand, caustic materials, etc. that are always present. When exposed to high temperatures, the belt scraper materials and biasing force elements must not deteriorate and lose their effectiveness.
It has been found that the blade mounts and the blades of the scraper may experience a considerable amount of vibration over a particular time period and with a large amplitude of vibration caused by the blades impacting mechanical belt fasteners. It is desirable to reduce the duration and amplitude of the vibrations in an inexpensive manner. It is further desired to provide a scraper blade and mount that dampens the vibration of the blades, while in use, and thereby increases their life against failure due to fatigue of the materials used.
Also, there is a need for a scraper blade system for scraping the conveyor belt that allows the belt to be reversed in the opposite direction and still provide a scraping of the belt bottom surface. The scraper blade system should provide the requisite force or pressure between the scraping blade and the belt, even though the wear occurs, by shifting the blade upwardly to take up the wear and to maintain the scraping pressure to remove the debris from the belt.